Plans to charge to deliver e-mail have come under fire from non-profit groups who said it could cripple fundraising.

Net giant AOL is introducing the charges to stop spammers as those who pay will bypass junk mail filters.

More than fifty groups including Oxfam America, Gun Owners of America and the AFL-CIO trade union have banded together to condemn the charging plan.

In a concession to the groups, AOL has said non-profit organisations will be exempt from the charges.

Mail room

In February AOL announced it was working with tech firm Goodmail to set up the certified e-mail charging plan for those that send millions of messages.

For small fees ranging from 0.25 of a cent to one cent per message, bulk e-mail senders could bypass AOL's junk mail filters and be sure that their messages get delivered to users.

AOL said the plan would reduce the amount of junk mail that people received because spammers were unlikely to pay the high fees required to get their messages to users.

Those that did not pay would have their e-mail treated as normal and risk it getting stuck in junk filters and marked as spam. Yahoo is also planning a similar service.

AOL's move sparked criticism culminating in early March with a group of more than 50 organisations banding together in a campaign to protest about the intention to charge.

The organisations protesting included the Democratic National Committee, The Electronic Frontier Foundation, Friends of the Earth and the MoveOn civic action group.

In an open letter to AOL, the non-profit groups protesting about the charging plan said it was a "threat" to a free and open internet.

Many of the groups in the campaign do much of their fund-raising and awareness work via e-mail and they fear this ability to reach supporters would be damaged by the charging plan.

The letter also warned that AOL was in danger of creating a two-tier internet; that AOL was levying a tax on e-mail and warned it could result in more junk mail for users.

The group said it counted more than 15 million people among its supporters, three million of which were AOL users.

In a late concession to the non-profit protesters, AOL has now said that they would not have to pay to have their messages included in the list of certified e-mail senders whose messages bypass filters.

AOL said it would pay the mailing fees on behalf of the non-profit groups to ensure messages get through.